This invention relates to a method of spinning yarn from two different types of staple fibers.
Previously this has been carried out using open-end spinning techniques, either by intimately blending the two types of fibers prior to yarn formation to form a yarn where the fibers of the different types are as far as possible distributed in a completely random fashion across the cross-section of the blend or by keeping the fiber types separate. This latter can be done using an open-end technique to form a so-called core-sheath yarn, where the core component is formed of one fiber type and a sheath component wrapped around the core, is formed by the other fiber type. Alternatively, on a ring frame two types of staple fibers can be fed to form a mock-grandrelle yarn, wherein the fibers of the two types, forming distinct components, wrap around each other in a manner similarly to the forming of a two fold yarn.
The present integral structure has the advantage unique that its properties of extension, strength and heat shrinkage are integrated and its different types of fibers are combined intimately in such a way so that the yarn resultant exhibits substantially uniform properties of a single, strand, just as though the strand had been formed with a single fiber type of staple fiber.
In the core-sheath structure of yarns of the prior art the properties of the two components sheath and core, each formed from a different fiber type remain separate and distinct from one another whereby, for example, the strength and heat-shrinkage of the yarn is adversely affected in what is known as two stage break, and also exhibits a nonuniform or differential shrinkage across the strand's cross-section. The past known core-sheath structure, however, has the major advantage that substantially all of the outside or sheath fibers are of one fiber type.
One example of the core-sheath method of yarn formation is disclosed in U.S. Pat. No. 4,130,983 (Barmag) which describes in column 2 a process in which, in a friction spinning apparatus, fibers of one fiber type form a core component and fibers of a second fiber type then are fed at a position axially displaced from that of the feed of the first type fiber to wrap around the core and form a sheath.